This invention relates to gravity outlets for railway hopper cars, hopper containers, hopper trucks and industrial bins.
One problem which has been encountered with regard to such outlets is their tendency to become partly open in transit an d/or during coupling in railroad applications.
Another related problem is that of particulate, particularly freely flowing dry powder lading leaking from the outlets in transit and/or during coupling.
These problems have been of sufficient concern to the railroad industry that among the requirements of the recently passed AAR specification for gravity outlets for railroad use is that the gate automatically lock in the closed position in the event of impact.
In regard to lading leakage, another requirement of the specification is that the outlet be able to retain 50 gallons of water in a 3 minute leakage test. This test is used as an indicator of relative "tightness" since it is more severe than any dry lading service condition and very repeatable.